1. Field of the Invention
The present invention relates to a scroll member assembly of a scroll-type fluid machine which is broadly used as compressors for air conditioning system, refrigeration chamber, refrigeration cycle and gas boosting system, as well as an expander for generating power through an expansion of a fluid.
2. Description of the Prior Art
The construction of scroll-type fluid machine, widely used as compressors and expanders, is well known to those skilled in the art.
This scroll type fluid machine has a pair of scroll members, each having an end plate and a wrap protruding therefrom, combined in such a manner that two wraps mate each other. One of the scroll members makes an orbiting motion relatively to the other but does not make rotation around its own axis. At the center of the end plate, provided is a high-pressure port which acts as a discharge port for discharging the high-pressure gas and an inlet port for a pressurized working fluid, respectively, when the fluid machine is used as a compressor and an expander, while a low-pressure port is formed at the peripheral part of the end plate.
Usually, the wraps of both scroll members have an equal shape, i.e. an equal scroll angle, and the closed spaces defined between two scroll members are in symmetry with respect to a point. Also, these spaces in the state of lowest pressure are formed at different distances from the low-pressure port. Therefore, the space remote from the low-pressure port in the state of lowest pressure is communicated with the low-pressure port to reduce the flow resistance encountered by the flow of gas and a suitable countermeasure is taken to avoid excessive heating of the gas by the wall defining the passage.
In order to minimize the flow resistance, the above-mentioned passage preferably has at large cross-sectional area as possible. The large cross-sectional area requires a correspondingly large diameter of the scroll members, and cause excessive heating of the gas in the state of lowest pressure.
Thus, the minimization of flow resistance and the reduction of diameter of the scroll members are incompatible with each other. It is quite difficult to simultaneously achieve both of these incompatible requisites, and no effective measure has been proposed up to now to meet this demand.